Allow sub-processes to request the DSL from danger

Author: orta

CHANGELOG.md

@@ -14,6 +14,11 @@
 ## Master
 
 - Adds `html_url` to the PR JSON declaration - [@orta][]
+- Adds a way for a sub-process to tell danger-js that it wants a copy of the DSL. This is a potential fix for when you
+  have a process that might not be ready to grab the DSL instantly from danger-js. The subprocess can print the message
+  `danger://send-dsl` to stdout and danger-js will re-send the DSL via STDIN. - [@orta][]
+
+These two are to try and figure out [danger/swift#108](https://github.com/danger/swift/issues/108).
 
 # 6.1.4
 

docs/usage/danger-process.html.md

@@ -1,6 +1,6 @@
 ---
 title: Danger in my Language
-subtitle: Using Danger Process
+subtitle: Using --process to build danger runners
 layout: guide_js
 order: 3
 blurb: How to use `danger process` to create a Danger runner for any language.
@@ -86,7 +86,7 @@ STDOUT.write(results.to_json)
 
 As Ruby is duck-typed, it doesn't need any infrastructure. You can parse the incoming JSON into an object, then work
 with the standard library to provide a Dangerfile environment. If you saved this file as `dangerfile.rb`, and
-`chmod +x dangerfile.rb` then you can run `danger process 'dangerfile.rb`.
+`chmod +x dangerfile.rb` then you can run `danger pr --process 'dangerfile.rb`.
 
 ### Tiny, and not too simple
 
@@ -192,6 +192,12 @@ It's pretty likely that your CI already has node, so it can just be `npm install
 
 Finally, let me ([@orta][]) know! I want to keep track of them all on the Danger Systems site :+1:.
 
+### Troubleshooting
+
+- If you're having timeout issues on waiting for STDIN from Danger JS, then it's possible that Danger JS is sending the
+  STDIN too soon for your process to catch it. To work around this, have your process print `danger://send-dsl` and
+  Danger JS will re-send the JSON to your process.
+
 [danger-swift]: https://github.com/danger/danger-swift
 [swift-json]: https://github.com/danger/danger-swift/blob/master/fixtures/eidolon_609.json
 [swift-stdin]:

source/commands/utils/runDangerSubprocess.ts

@@ -11,6 +11,10 @@ import { RunnerConfig } from "../ci/runner"
 
 const d = debug("runDangerSubprocess")
 
+// If a sub-process passes this to stdout then danger-js will pass
+// the DSL back to the process
+const messageToSendDSL = "danger://send-dsl"
+
 // Sanitizes the DSL so for sending via STDOUT
 export const prepareDangerDSL = (dangerDSL: DangerDSLJSONType) => {
   if (dangerDSL.github && dangerDSL.github.api) {
@@ -38,25 +42,39 @@ export const runDangerSubprocess = (
   d(`Running subprocess: ${processDisplayName} - ${args}`)
   const child = spawn(processName, args, { env: { ...process.env, ...config.additionalEnvVars } })
 
-  d(`Started passing in STDIN`)
-  child.stdin.write(dslJSONString)
-  child.stdin.end()
-  d(`Passed in STDIN`)
+  const sendDSLToSubprocess = () => {
+    d(`Started passing in STDIN`)
+    child.stdin.write(dslJSONString)
+    child.stdin.end()
+    d(`Passed in STDIN`)
+  }
+
+  // Initial sending of the DSL
+  sendDSLToSubprocess()
 
   let allLogs = ""
   child.stdout.on("data", async data => {
-    const stdout = data.toString()
+    const stdout: string = data.toString()
     allLogs += stdout
 
-    // There are two checks
+    // Provide a way for a process to request the DSL
+    // if they missed the first go.
+    if (stdout.includes(messageToSendDSL)) {
+      sendDSLToSubprocess()
+    }
+
+    // There are two checks for a response
     const maybeJSON = getJSONFromSTDOUT(stdout)
     const maybeJSONURL = getJSONURLFromSTDOUT(stdout)
 
     // Remove message sent back to danger-js
     const withoutURLs: string = data
       .toString()
       .replace(maybeJSON, "")
+      .replace(maybeJSONURL + "\n", "")
       .replace(maybeJSONURL, "")
+      .replace(messageToSendDSL + "\n", "")
+      .replace(messageToSendDSL, "")
 
     console.log(withoutURLs)